Automatic railroad signaling and control system



193,7. 0. w. w. PRESCOTT 2,098,401

AUTOMATIC RAILROAD SIGNALING AND CONTROL SYSTEM Filed Sept. 15, 1954 e Shets-Sheet 1 Nov. 9, 1937. c. W. W. PR

ESCOTT AUTOMATIC RAILROAD SIGNALING AND CONTROL SYSTEM Filed Sept.

6 Sheets-Sheet 2 NOV. 9, 1937. c w w TT 2,098,401

AUTOMATIC RAILROAD SIGNALING AND CONTROL SYSTEM Filed Sept. 15, 1934 I 6 Sheets-Sheet 3 /09 86 70 /02 8 8 3 8 //5 m 87 79 /30 //a 76 74 75 I 77 I 3 as 82 Nov. 9, 1937.

AUTOMATI C C. W. W. PRESCOTT RAILROAD SIGNALING AND CONTROL SYSTEM Filed Sept. 15, 1934 6 Sheets-Sheet 4 Nov. 9, 1937. c w w p 5o 2,098,401

AUTOMATIC RAILROAD SIGNALING AND CONTROL SYSTEM Filed Sept. 15, 1934 6 Shets-Sheet 5 5 we 7 Us 8 I l m- ,1937. c. w. w. PRESCOTT 2,093,401

AUTOMATIC RAILROAD SIGNALING AND CONTROL-SYSTEM- Filed Sept. 15, 1934 6 Sheets-Sheet 6 Patented Nov. 9, 1937 PATENT OFFICE .AUTOMATIC RAILROAD SIGNALING AND CONTROL SYSTEM Charles William Walker Prescott, Pymble, Australia Application September 15, 1934, Serial No. 744,233

17 Claims. (01. 2466) This invention relates to railroad signaling and has particular reference to such types of signaling devices and systems which incorporate an indicator carried by the locomotive or vehicle it- .5 self, in place of or in conjunction with roadside signals. o

The primary object of this invention is to provide means whereby an indicator carried on the locomotive'will give the driver a continuous in- 10 dication of the maximum speed at which the train may safely be driven (termed track speed) which indication will automatically vary from time to time according to the condition of the track ahead. Having such essential indica- 15 tion, it is a matter of ease for the driver to operate the train with certainty at the correct speed from the point of view of safety and of utilizing the track to maximum capacity-by means of the said track speed indicator used in conjunction with a train speed indicator.

The most important factors influencing the track speed are:

(a) The length of unoccupied track aheadof the train;

(b) The gradient and/or curvature of that track;

The braking characteristics of the train itself, and these factors are continuously employed in conjunction in the present invention to actuate the track speed indicator. Other minor factors may be employed if desired in a similar manner, and in the case of long lengths of level track, factor (b) may be'omitted.

The first two factors mentioned are dependent 35 upon the instantaneous condition and nature of the sections of the track ahead of the train, and are conveyed to the locomotive track speed indicator by means of electric currents imposed upon the rails. The third factor, that of the braking 40 characteristics of the train, is one which has always caused considerable difiiculty. It has previously been proposed to provide certain mechanical means to approximate changes of this factor, but relatively few fixed settings were available,

40 which at best were approximations, and hence no accurate indication of permissible track speed for all make-ups of trains was practicable. In the present invention, however, this factor which varies with the train make-up, is accurately and 50 readily set in the instrument itself, and will combine with the other factors to give an accurate indication of permissible track speed for each particular train. On lines used only by trains of standard make-up this adjustment may be dis- 5 pensed with. The varying track gradient (and curvature) factor which affects the braking of the train is ingeniously combined with the set braking characteristic factor to cause an alteration of the track speed indicator whenever the former factor is altered. 5

With regard to the factor of the length of unoccupied track ahead of the train, the electric current put on the rails has a frequency which is proportional to the square root of the length of clear track ahead of the train. The expression frequency employed in this specification is intended to cover coded or "interrupted current, both A. C. and D. C.

Thus the invention gives the driver all the essential information, namely permissible track speed and actual train speed, in a very simple form on the locomotive, and by a comparison of these two speeds he is thus enabled readily to operate the train in the most safe and efficient .manner entirely independently of roadside signals, and hence in all weathers. The advantages thus gained as regards the utilization of the track to maximum capacity by various types of train are obvious.

Various refinements of the fundamental invention may be employed, for instance colour indications (or a warning) may be given when the train speed is below, in the zone of, or above the track speed. If desired this colour-comparison of the two speeds may entirely replace one or both of the actual speed indications.

Furthermore, the invention may be employed not only as an indication to the driver, but as an actual automatic train control which will function more completely than such controls hitherto known, even to the extent of push-button operation of the train by an unskilled operator in the case, of electric trains. Automatic brake application may be employed, either with or without time element or forestalling factors.

The invention may be carried into effect with different forms of apparatus, but a preferred embodiment thereof is now described. The electrical system .incorporates some features known in automatic signaling and is shown in .diagrammatic form which is usual in such systems and which will be clearly understood by those skilled in the art.

In the drawings,

Figure 1 is the track circuit wiring diagram,

Figure 2 is the locomotive and instrument wiring diagram,

Figure 3 is a front elevation of the locomotive instrument.

Figure 4 is a rear elevation of the instrument,

'I--'I of Figure 5,

Figure 8 is a cross-sectional elevation of a detail, on line 8-8 of Figure 6,

Figure 9 is an example of a frequency table,

Figure 10 is a locomotiveand instrument wiring diagram for a modified form of the instrument,

Figure 11 is a fragmentary plan view, in part cross-section, of a modified form of the instrument,

Figure 12 is a side elevation taken on line I2--I 2 of Figure 11,

Figure 13 is a side elevation taken on line I3-I 3 of Figure 11, and

Figure 14 is a rear elevation, taken, on line ll-H of Figure 13.

Figure 1 shows the means by which the various frequencies are imposed on the rails, which frequencies are picked up by a train by induction to actuate the instrument and give the indication of the condition of the track ahead, in terms of a permissible track speed in miles per hour.

Two sets of currents are'imposed on the rails of each track circuit, one being in the opposite direction in the two rails, and having a frequency which is dependent upon, and a function of, the square root of the length of the clear track ahead of this circuit. A method of obtaining the frequencies required for various. lengths of clear track is given hereinafter, it being sufficient now to explain that after that length of track in which the worst braked train may be stopped (the safe length) is clear, a standard frequency is imposed on the rails of a track circuit.

The other current imposed on the rails travels in the same direction in both rails, and its frequency varies in different track circuits according to the gradient of the .clear length of track ahead, and according to the curvature of that track. A method of obtaining these frequencies for different sections of the track is also given hereinafter.

Figure 1 shows a number of adjacent sections A, B, C and D of the track, the insulated rails I, 2 of which are divided into track circuits by insulators 3, 3, as in known practice. The various track circuits are fundamentally similar, and the train is considered as traveling from right to left.

The current having a frequency which is determined by the length of clear track ahead (termed clear-track frequency) is fed into one end of track section D from the secondary 4 of a transformer by leads 5 and 6 to the rails I and 2 respectively. An adjustable rheostat or impedance I controls the maximum current.

The usual track relays 8 and 9 of track cir- I cuits A and B are duplicated, through leads I and II, by repeater relays I2 and I3 (fed from a source of supply in known manner), grouped with relay I4 associated with track section C. The relay of section D is indicated by I4 Presuming that sections- A, B and C are unoccupied, relays I2, I3 and I4 will be energized and their armatures will close contacts I5, l6 and I1 respectively, as shown in Figure 1. Thus a circuit is established from a positive source of supply, through the closed contacts II, I6 and I5 and lead l8 to the vibrating contact I9, which is connected to the negative lead of the source of supply. Thus the vibrating contact I9 is actu-v ated. This vibratingcontact I9 and also vibrating contacts 20 and 2|, are of the known type which will oscillate at one frequency only when energized, these contacts having a common negative return lead I9. Presume that contact I9 oscillates at 50 vibrations per second, then its oscillations will cause contact 22 to be closed 50 times per second, and hence current flowing from supply 28 through lead 40 and the vibrator I8 to contact 22 is interrupted or "coded 50 times per second. From contact 22, this current having a frequency of 50 impulses per second is carried by leads 23, 24 and 25 to the grid 26 of the thermionic valve 21, the filament of which is connected to the negative terminal of battery 28. Then current from supply 29 will flow through valve 21 with a frequency of 50 impulses per second, which current is carried by lead 38 through contacts I1 [6 and I5 which in the present positions are closed by armatures coupled to the armatures of relays I4, I3 and I2, in known manner. From contact! 5 the coded current is carried by lead 3| to the primary 32 of the transformer incorporating secondary 4, said primary 32 being also connected to supply 28. Consequently a 50 cycle current from secondary 4 is supplied to rails I and 2 of section D, and flows in opposite directions in these rails. This frequency will be picked up by a train entering section D.

If; now, section A is occupied relay 8 is short circuited and hence the armature of repeater relay I2 drops, opening contacts I5 and I5 and closing the opposite contacts-15" and IS. The relays l3 and I4 remain closed, and hence the circuit to vibrating contact I9 is broken, while a circuit from the positive source through contacts IT, IS and hi and lead 33 is established to vibrating contact 28. This contact 20 will vibrate only, say, at 70 vibrations per second, and interrupted encoded current from contact 34 is supplied through leads 24 and 25 to grid 26 of valve 21. Hence the valve delivers current of a frequency of 70 impulses per second to lead 38, whence it passes by contacts I1 I6 and I5 to lead 35 and to a tapping on transformer primary 32. From the secondary 4, a current of '70 cycles is delivered to the rails I, 2 and is picked up by a train entering section D.

Similarly, it will be clearly seen that if section B of the track is occupied, relays 9 and I3 will be de-energized, and hence contacts I3 and I6 will be opened and their opposite contacts I8 and It will be closed. This results in vibrating contacts I9 and 20 being inoperative, and vibrating contact 2| being supplied with energy from the source through contacts I! and I6 and lead 36, which vibrating contact 2| impresses a current interrupted (say) 90 times per second upon the grid of valve 21. Thus a current having a frequency of 90 impulses per second is impressed by valve 21, through lead 30 and contacts I1 and I 6 and lead 31 onto a second tapping of transformer primary 32, from the secondary 4 of which the 90 cycle current is passed into rails I and 2 of section D.

From the foregoing it will be seen that the particular frequency impressed on the rails of any track circuit is a function of the length of the clear track ahead of that section, and will be automatically varied as variations occur in that length of clear track.

The particular arrangement described for feeding track circuit D is repeated for all the other track circuits of the line, as is usual in high speed signaling.

Figure 1 also shows the manner in which the gradient and curvature current is fed into section D. The particular frequency fed into a track circult is automatically varied according to the overall gradient and/or curvature of the length of the clear track ahead of that circuit. Whi1e sections A, B and C are clear, contacts l 8 and I1 are closed by armatures coupled to those of relays l3 and M, and current from'a supply is taken through these contacts and lead 38 to a vibrating contact 39 which oscillates (say) 50 times per second, and which has a negative return lead 39 Thus current from source 28 is fed by leads 40 and 4|, coding contact 32 and lead 43 to grid 44 of thermionic valve 85, which is in turn fed by lead 48 from source 28. Since the input to grid 44 is coded at 50 impulses per second, current at this frequency passes from valve 85 by lead El to the primary 48 of a transformer, and'50 cycle current will flow from the secondary 89 of this transformer through the usual rail-to-rail impedances 58, 58 to flow in the same directions in rails l and 2, and to be picked up by a train entering section D. Section A is regarded as having the same gradient as section B, and is not provided with a special gradient oscillator.

If, now, section B is occupied, relays 9 and I8 are de-energized, and contact 5 is opened and contact I6 closed. This results in the disconnection of vibrating'contact 39 and the energization of vibrating contact 5i from the source through contact H and lead 52. Contact 5| has. say, a period of 40 vibrations per second, and hence grid 84 is energized with this frequency, and hence valve 85 (throughtransformer 48, 49) will deliver 40 cycle current to the rails, I, 2.

Thus it will be seen that if sections A and B are clear of traflic, vibrating contact 38 is in operation. If, however, section B is occupied ahead of a locomotive, vibrating contact 38 is cut out of operation and vibrating contact 5i is in operation, as above described.

All track circuits are fed in the same manner, the number of frequencies required for each section being dependent upon the physical nature of the sections ahead, up to the safe length of clear track.

Figure 2 shows they manner in which the two frequencies imposed on rails l and 2 are picked up by the locomotive. Two similarly wound collector coils 53 and 58 are connected in'series in such manner as to be energized (by inductance) by currents in opposite directions in rails I, 2 in known manner. Leads 55 and 58 connect these coils to an amplifier 51 which is connected by leads 58 and 59, through a proving relay 60, with another part of the apparatus (hereinafter described).

Collector coils 8! and 82 are so connected that they will be energized only by currents in the same direction in rails I, 2 and these coils are con- The face of the instrument is shown in Figures 3 and 5, and includes two ground glass windows 18 and H, one of which is marked Track and upon which the maximum permissible track speed for the particular train is indicated, and the other of which is marked Train", upon which the actual train speed is indicated. A miles-per-hour scale 12 is located between the two windows. The instrument is covered by a detachable top 13.

As seen in Figures 5 and 6, two parallel slide rods 14 and 15 are mounted at their ends in standards 16 and 11 and slidable thereon is a carriage 18 carrying a lamp 19. The carriage 18 is engaged by a rotatable screwed rod 88 (Figure 5) by the rotation of which it is progressed along rods 14 and I5, in either direction.- As shown in detail in Figure 8, lamp I9 is fed through a contact 8| wiping on energized rod 15 and connected to one terminal of the lamp while the other terminal feeds through wiper 82 onto a rheostat 83. Lamp 19 is for the purpose of illuminating window I0, and in order that its intensity on this window (and on an adjacent light sensitive strip hereinafter referred to) may remain constant during its displacement towards or from the win-' dow on rods 14 and 15, the rheostat 83 is employed to suitably increase the light intensity as the lamp retracts from the scale, and vice-versa.

Mounted on base 69 is a frequency meter 84 of known type, which rotates a pinion 85 meshing with a spur wheel 88 carried on shaft 81. 'Connected to spur 86 is an arcuate screen 88, which is formed with an arm 89 mounted in a bearing 90 (Figure 5). the light from lamp l9, and by its position to regulate the height of the beam from this lamp passing under it and illuminating window"). In Figure 6 the screen 88 is shown at its lowest position, and it will be seen that the higher screen 88 is lifted by counter clockwise rotation of spur 88, the higher will be the illumination on window ill, and hence the higher will be the M. P. H. indication'of track speed on this window. A fixed screen 9| prevents light from lamp T9, in the retractecrposition, passing over screen 88.

Frequency meter 84 is connected to leads 58 and 59 from amplifier 57 (Figure 2) and hence the position of screen 88 is determined by this frequency meter, which in turn depends upon the clear track frequency picked up from the track circuit, this frequency being a function of the length of the clear track ahead of the section occupied by the train. The greater the length of the clear track, the higher Will be the position of screen 88, and hence the higher the indication in M. P. H. given on window 18 (up to a certain minimum safe distance) other factors remaining constant. The other two factors, gradient (and/or curvature) of the track and the braking characteristics of the train, are combined with the clear track distance in the instrument by adjustment of the position of lamp 19 along its mounting rods. It will be obvious that for any position of screen 88, the indication thrown on window 10 by lamp 19 will decrease if the lamp The function of screen 88 is to shield is retracted from the window, and vice versa.

the safe track speed. These adjustments are effected as now described.

As shown in Figure 5, rod 80 has mounted thereon a spur wheel 92 which is driven by the pinion 93 of a. reversible motor 94. A high reduction train is employed consisting of pinion 95, spur wheel 96, pinion 91, spur wheel 98, pinion 99 and spur wheel I00, the ratio being such that motor pinion 93 rotates spur wheel 92 sufllciently to move carriage 18 from one end to the other of rods 14, 15 while spur wheel I00 makes less than one revolution. Shaft 80 is continued through the gear train and is fitted with a knob IOI for the initial manual setting of carriage 19 according to the braking characteristics of the train. g

A controller which actuates motor 94 is best seen in Figures 4, 5, 6 and 7. Thisco'ritrqll er includes a ,disc I02 having mounted in its rinr' a plurality of spring loaded contacts I03 which representvarious braking percentages and which are not evenlyspaced on this account. The contacts I03 are, however, connected by leads I04 to a plurality of evenly spaced plug sockets I05 on the face of the disc. I02.

Disc I02 is mounted for rotation in bearing I06 on standard I01, and is connected to spur wheel I00 to rotate therewith. A number of contacts I03 engage'under two contact shoes I08 and I09 in any working position of disc I02, and these shoes are insulated from each other by an insulator H0, and end respectively in terminals III and I I2 which are connected by leads I I3 and I I4 (Figure 5 to the two field windings of the reversible motor 94, which motor is also connected to the negative terminal of a source of supply in known manner.

The various sockets I05 represent various retardation percentages such as 5%, 6% and so on, and the controller operates as changes in gradients (or curves) affect this retardation percentage, either decrease or increase. 'Presuming that two steps of 1% on either side of level only will be met on the track, five of the contacts I03 will be employed. The contact representing the retardation percentage of the train (as made up) on level track is brought under insulator H0, and a five point plug H5 is plugged into sockets I05 connected to this particular contact and the two on either side thereof. The plug I I5 is connected by flexible leads II6 to terminals II1 on standard I01, and these terminals are in turn connected by leads II8 (Figure 5) to five adjacent contacts II9 of a known type of contact-making .frequency meter I20.

Frequency meter I20 is connected to leads 61 and 68 of the amplifier 65 (Figure 2) fed by the gradient frequency imposed on the line, and is .also connected to the positive terminal of the source of supply in known manner.

The operation of this last described portion of the device is as follows:

The rod 14 is calibrated (by a method hereinafter explained) with various percentages repre senting the retardation of various trains. The braking characteristic or percentage having been determined by the make-up of the train, finger knob IOI is manually adjusted to set carriage 18 to this percentage, which adjustment will simultaneously bring the contact I03 of the controller representing this retardation percentage under insulator IIO, by the medium of the gear train. Plug H5 is then inserted to engage the socket I05 connected to this centralized contact I03, and two sockets I05 on either side thereof.,

During the journey, the contact making frequency meter is influenced by the varying frequencies impressed on the rails according to gradient, and will therefore from time to time connect one or other of the contacts II9 to a source of supply Thus, through leads H0 and H6, one or other of the five engaged contacts I03 is energizedfrom the source. While only the central contact I03 (under insulator H0) is energized, no effect is felt, but when a contact on one side of-this central contact is so energized, current passes therethrough to (say) shoe I08, and by lead I I3 to one field coil of reversible motor 94. The motor then sets the gear train in motion, rotating rod 80 to retract lamp 19 from window .10 for a reduction in effective retardation due to a. down gradient, and reversely for an up gradient.

The motor also sets the gear train in motion,

' the direction of rotation being such as to bring the energized contact I03 under insulator H0,

which as soon as achieved, cuts off supply to the motor. The mechanism remains in this position until a fresh frequency due to gradient afiects frequency meter I20 to change its contact H9 which is energized from the source, and so set motor 94 in motion again, to readjust lamp 19.

Thus it will be seen that the light thrown by lamp 19 on to window 10 to indicate the maximum permissible track speed is adjusted ((1) according to the braking characteristic of the train, by initial setting of carriage 18, (b) according to length of clear track ahead of the train, by the clear track frequency adjusting the position of screen 08, and (0) according to gradient and/or curvature of the clear track ahead, by the gradient (and/or curvature) frequency causing an adjustment of the position of lamp carriage 18 during the journey.

The permissible track speed for the particular train being shown on window 10, in M; P. H.

against scale 12, it is now required that the adjacent window 1| be illuminated to a height representing instantaneous train speed. Having these two speed indications against scale 12, it is a matter of ease for the driver to maintain his train speed in the zone of the track speed, and thus utilize the track to maximum capacity, but with safety, since he canalways stop his train should an obstruction occur, providing his train speed is not greater than the track speed.

The manner in which the train speed indication is thrown on window H is illustrated in Figures 5 and '1. Three stationary lamps I2I, I22 and I23 are arranged transversely on the instrument, and are adapted to illuminate window 1|. A centrifuge (speedometer) I24 is mounted on base 69, and operates a pinion I25 which in turn rotates a spur wheel I26, on which is mounted an arcuate screen I21 normally disposed between lamps I2I, I22, I23 and window 1I. Spur wheel I26 is freely rotatable on shaft 81, and an arm I28 extending from screen I21 is taken to a bearing I29. An increase in train speed causes speedometer I24 to lift screen I21 and so permit a higher beam of light to pass from'lamp I 2I, I22 or I23 to window 1I, thus indicating an increase in train speed against scale 12. In the drawings, screen I21 is shown in its lowermost position.

By this means the actual train speed is given on window H for comparison with the track speed on window 10.

Automatic brake application means are provided, whereby the brakes are applied if and when the train speed exceeds the permissible track speed. The usual time lag would, of course,

be incorporated. Furthermore, assistance is given the driver (and by repeater lights, the fireman) by colouring the train speed indication on window 1| green,'yellow or red, according to whether it is below, in the zone of, or above the permissible track speed. The manner in which these operations are carried out is best illustrated by Figure 2.

Adjustable lamp 19 also liluminates a lightsensitive strip I30, adjacent window 10 (see also Figures 5 and 6) and a lamp I3I aligned with lamp I2I (Figure 5) illuminates an identical light-sensitive strip I32. These light-sensitive, strips are of known type in which their resistance varies according to the length of them which is illuminated- The reason for adjusting the intensity of light from lamp 19 according to its position in relation tothe front of the instrument (and hence in relation to strip I30) will now be clear.

Light-sensitive strips I30 and I32 are respectively connected by leads I33 and I34 to the two windings I35 and I36 of a differential three position relay I31 (of known type) these wind,- ings also being connected by lead I35 to a source of supply. The other terminals of the strips are connected by leads I38 and I39 respectively to two proving relays I40 and MI in turn connected to the negative terminal of the source.

The lengths of light strips I30 and I32 which are illuminated (and consequently their resistances) are dependent upon the positions of screens 88 and I21 respectively. When the track and train speeds are equal, the heights of the train and track light beams are equal, and hence the resistances of strips I30 and I 32 are equal, and relay I31 is not moved from its normal position wherein contacts I42 and I43 are closed through arm I44, while contacts I45 and I46 are open. Current flows from a source, through contact I42, arm I44, contact I43, lead I41 and through the upper winding of a double-Wound 7 relay I48, either winding of which is sufficient to operate the relay, and energization of which holds contact I49 open. From relay I48 the current flows through relay I50 to the negative to the source, thus energizing its contact. I5I and supplying current from the source to lamp I2I, which feeds back by lead I52 through a proving relay I53.

Lamp I2I, as shown in Figures 5 and '1, is covered by a yellow glass I54, and hence the train speed. indication thrown on window 1| is coloured yellow.

If, now, the train speed should increase over the track speed, the resistance. of strip I32 is decreased over that of strip I30, and hence more current will flow through winding I36 than through winding I35 of the difierential relay I31. When this'diiference is sufficiently great to actuate the relay, flexible arm I44 is moved (in known manner) to open contact I43, while the other contacts thereof remain unaltered. This results in the de-energization of relays I48 and I50, thus closing contact I49 and so connecting lamp I22 to the source, and opening contact I5I and extinguishing lamp I2I. The. circuit of lamp I22 is completed to the source through lead I56 to relay I51, the purpose of which is hereinafter explained.

Lamp I22 has a red glass I58 (Figure 5) about it, so that the train speed indication on window 1| is coloured red, giving warning of excess of train speed over track speed.

When the train speed drops below track speed, greater current will flow in winding I35 than in winding I36 of relay I31, and arms I44 and I59 of the relay will move to open contact I42 and close contacts I45 and I46. Supply from a source now flows through contacts I45,'I46, lead I60, the second winding of relay I48 (holding contact I49 open) and relay I6I to close contact I62. Thus the positive supply is connected through contact I62 and lead I63 to lamp I23, which completes its circuit through lead I52 to relay I53 and thence to the source. Thereby only lamp I23 is illuminated, and this lamp is covered by a green glass I64 (Figure 5) so that the train speed indication on window 1| is coloured green, readily indicating that the train speed is below the track speed.

It is to be noted that the colouring of the train speed indication to readily show its relation to the track speed is considered secondary only to the actual M. P. H. indications of the two speeds given on windows and 1|. In the event of the fireman requiring an indication of these relative speeds, repeater lamps I2I I22 and I23 are connected in parallel with lamps I2I, I22 and I23 across the supply, and are placed conveniently for the fireman.

The circuit for the automatic application 01' the brakes (with the usual time lag) in the event of train speed exceeding track speed by a certain amount, is also shown in Figure 2. Lamps 19 and I3I are fed from a positive source andcomplete their circuits through leads I65 and I66 to two windings respectively of a double winding relay I61, energization of both of which windings is necessary to maintain its contact I68 closed. These circuits are completed by a common lead I69 through a contact I10 actuated in common with contact I10 of proving relay 60, and through a contact I1I actuated in common with contact I1I of proving relay 66, and thence to the negative of the source.

Proving relays I40, MI and I53 have contacts I12, I13 and I14 respectively, closed on energization of these relays, and proving relay I 51 has a contact I which is opened on energization of this relay.

The brake circuit is from a source, through contacts I13, I12, I68, I15, I14, I10 and "I to an electro-pneumatic valve I16 (of known type) to the negative of the source, said valve holding the brakes off while energized. While lamps 19 and I3I are lighted, strips I30 and I32 energized, either yellow lamp I2I or green lamp I23 lighted, and amplifiers 51 and 65 operating, the circuit to valve I16 is complete, and the brakes are held off. However, should one of these units fail, its associated proving relay will be de-energized and the valve circuit opened, thereby applying the brakes. Similarly, should train speedexceed track speed by a certain amount, relay I51 will be energized and contact I15 opened,

thereby interrupting the valve circuit and again applying the brakes automatically, until train speed drops sufliciently to close contact I15 once more, when valve I16 may release the brakes once more.

A partition I19 (Figure 5) prevents interference between train and track lamps, and a second partition I80 segregates. the effect of lamp I3I operating light-sensitive strip I32 from the rays of lamps I2I, I22 and I23.

Although in the foregoing description one oi the currents is described as traveling in the same direction in both rails, while the other travels in different directions in the two rails, it is contemplated that the two currents may be superimposed, and travel similarly in the rails, by suflicient difierentiation in frequency, in which case the pick-up instrument on the locomotive would necessarily discriminate between currents in diflerent wavebands.

Frequency calculations of that length.

Let it be assumed that the worst braked train to be used on the track has a retardation value of 3% (expressed as a percentage of train weight) at its maximum speed, and that the retardation of the best braked train is 10%. Further, that the maximum track gradients do not exceed 2%.

Use is made of the well known formula Where D=stopping distance in feet.

V=speed in M. P. H. at which brakes are applied Rt=equivalent retardation due to brakes and friction (expressed as of weight of train) Rg=equivalent retardation due to gradients and/or curves (curves being expressed as gradients, that is. The extremes of retardation will then be:

3%2%= 1% and 10% +2%=12% As the minimumretardation is so low, steps of /2% are used in adjusting for Ry.

In the above formula, if V is taken at 50 M. P. H. and Rt-i-Rg at 1% then D=8333 ft. that is, the most poorly braked train traveling at 50 M. P. H. requires 8333 feet in which to stop after application of the brakes, and this is consequently the maximum length of the trackahead of any track circuit concerning which it is necessary to apply condition indications by various frequencies to this track circuit.

As previously stated, the clear track frequency (in) must be proportional to the square root of D. A convenient scale is given by the arbitrary Scale M D (feet) 300 500 1000 1500 2000 in (cycles)- 90. 52 87.76 82.68 78.8 75.5

D (feet) -3000 4000 5000 0000 8333 i In (males)- 70 65.35 01.3 57.0 60

According to the lengths of the track sections (up to 8333 ft.) ahead of any track circuit, the various frequencies which it is necessary to provide by vibrating contacts I0, 20 and 2| (Figure 1) are determined as above. For all clear track", that is a clear distance of 8333 ft. or more, only a vibrating contact having a period of 50 oscillations per second (such as- I9) (or a direct 50 cycle A. C. supply, if available) would be in operation, but if the clear distance is less than this figure, special frequencies would come into operation.

The frequencies (fa) applied to the track sections representing gradient and/or curvature may be arbitrarily chosen, a convenient scale being:

Scale N M 10 20 a0 40 so 00 70 (Note: The previously described construction shows only two points of adjustment on either side of level, but obviously more may be employed if desired).

The required gradient frequencies, selected as above, are employed on track circuits as before explained, and are applied by vibrating contacts such as 39 and 5| (Figure 1). Figure 1 being V: .3D(Rt+Rg) (3) Assuming D=3000 ft. which from the scale M above gives frequency ,fn=70 cycles per second, and by employing various values for Rt+Rg (indicated below by R) the following scale is obtained:

Scale 0 R(%) 1 1% 2 2% 3 3% 4 4 5 V(M. P. H.) 30 36.75 42.42 47.4 51.96 57.1 60 63.6 R(%) 5 5% 6 0% 7 7% s 8% V(M. P. H.) 00.9 70.35 73.5 70.5 79.3 82.1 84.9 87.3 R'(%) 9 9% 10 10% 11 11 5 12 v(M. P. H.) 90 92.4 94.9 07.2 99.45101.7103.95

Since a frequency of 70-cycles has been chosen for setting purposes, screen 88 (Figure 6) is rotated to the position it will occupy when energized by 70 cycle current from the rails. The train braking characteristics having been determined from the train make-up at (say) 4%, which. from the scale 0 is equivalent to 60 M. P. H., finger knob IN is rotated to move lamp 1!! to a position wherein its rays will illuminate window 10 up to the 60 M. P. H. division. This position is marked on rod I4, or on controller disc I02, for future settings of 4% trains. Similarly, by adopting other values of R from (say) 1% to 12% in scale 0, the rod 14, or disc I02, may be completely calibrated, and it will then be a matter of facility to make future settings on the instrument for various values of retardation percentages for various values of train make-up.

It is to be noted that the gearing between screwed shaft 80 and controller disc I02 is such that for every position of carriage 18 of (say) V variation of retardation, one of the contacts I83 is under insulator IIO, thus synchronizing these units.

A summary of the foregoing calculations is given in the form of a table, calculated for a hypothetical length of track, in Figure 9.

This track consists of sections- E, F, G, H, J, K and L of the various lengths given thereon, and the train is considered as moving from right to left. The frequency for clear track (f) and for gradient (Io) calculated for each section of the track according as to whether one, two or more sections ahead are clear, are applied to the immediately preceding track section, as in known practice.

Taking section E as typical, values of In for one, two and three tracks clear ahead are obtained from scale M, which gives these frequencies for various lengths of clear track. The gradient frequency ,fG is obtained by dividing the total velocity head by the length of clear track in hundreds of feet. In column E with two tracks ahead clear:

A rise being taken to the nearest lesser this is taken as /z% (rise), which from scale N gives f 3=60 cycles. Similarly a fall is taken to the nearest greater /2%, for the sake of safety.

It will therefore be clear from the foregoing that the various frequencies required for indicating length of clear track ahead, and for the gradient and/or curvature of the line, may be readily calculated and applied to the rails of each track circuit, and as readily picked up therefrom and employed in the locomotive instrument. Moreover, since the frequencies applied to one track circuit are in respect of the next and succeeding track sections, the driver will always have the time taken in. one track circuit to act on the indicator readings.

The invention therefore provides the essentials of a most complete form of locomotive or rail vehicle indicator, which may also be employed to give automatic brake control. The roadside apparatus is simplified, and it enables a vehicle driver to make the maximum safe speed over any section of the track, thus utilizing the permanent way to the greatest possible degree under all conditions and weathers, and by all types of trains.

In certain cases it may be desirable to replace the electric method of colouring the train speed indication by mechanical means, which are cheaper of construction and result in a simpler electrical circuit. Such mechanical means are shown in Figures 11, 12, 13 and 14 which illustrate the instrument heretofore described, with mechanical differences.

Referring particularly to Figures 11 and 12, the saddle 18 is mounted on the rails 14 and 15, and is actuated by screwed rod 88 as previously. Pins I8! and I8I on either side of saddle 18 pivotally engage respectively in elongated slots I82 and I82 of parallel arms I83 and I83 which at their forward end carry an arcuate screen 88 A cross rod I84, secured in spur wheel 86 driven through pinion 85 by the frequency meter 84, passes through arms I83, I83 and is supported by arm 89 journalled at 98. Thus it will be seen that rotation of spur wheel86 due to actuation by frequency meter 84 causes rod I84 to swing arms I83 and I83 upwardly about pivot points I8I and HP, thus raising the screen 88 It will also be seen that adjustment oi saddle 18 towardsor from front window by rotation of screwed rod 80 from the means hitherto described, will result in an increased or decreased lift respectively of the screen 88 for a given movement of the fre quency meter. supplied from a lamp I85 mounted on bracket I86 secured to the framing.

The operation of this form of the track speed indicator is similar to that previously described.

The mechanical means of colouring the train speed indication according to its relation to the instantaneous value of the track speed, is best illustrated in Figures 11, 13 and 14. Spur wheel I26, driven through pinion I from a frequency meter as previously described, has mounted thereon a drum I81, apertured towards its front side as at I88,'which forms a screen for the passage of light from a vertically disposed battery of lamps I89, I90 and I9I on to window H to give the train speed indication thereon. Formed in horizontal alignment across the back face of drum I81 are three spaced apertures I92, I93 and I94 which are glazed green, yellow and red respectively, and through any of which rays from lamps I89, I90 and I9I may pass to illuminate window H to a height which is determined by the instantaneous position of the upper edge of aperture I88 in the front of drum I81.

The selection of which of the coloured apertures the rays pass through is carried out by shielding, which in turn is dependent upon the instantaneous relation between the track and train speeds, that is the angular relation between screen 88 and drum I81.

At the forward extremity of arm I83 (Figure 11) is a pivotal connection I95 between this arm and a lever I96 which is journalled at I31 and is returned through an aperture I98 in partition I19 and carries an arcuate shield I99 disposed about the rear face of drum I81. Shield I99 is of the shape shown in Figure 14, being of generally rectangular shape which is slotted out at the right top corner at 200, and at the lower left corner at 2!, these slots being in vertical register respectively with coloured apertures I92 and I94 in drum I81. Centrally shield I99 is apertured at 282 in vertical register with coloured aperture I93 in drum I81.

The operation of this shielding devica,is readily seen from Figures 13 and 14. In Figure 1.4 shield I99 is in the position relative to drum I81 which it will occupy when the train and track speeds are equal, and it will be seen that rays from the lamp I89 in this relative position will pass through aperture 202 in shield I99, and through the yellow aperture I93 only in the drum, and hence illumination thrown on to window 1I will be coloured yellow, indicating the equality of the train and track speeds. In this position the green and red apertures I 92 and I94 are blanked off by shield I99, and no light passes therethrough.

If, now, the track speedrises above train speed, shield I99 will be moved downwardly in relation to drum I81, and as will be seen from Figure 14, apertures I93 and I94 will be blanked by the shield, and slot 200 therein will expose green aperture I 92 to the lamp rays, thus colouring the train speed indication green to indicate the excess of track speed over train speed.

Similarly, if track speed. drops below train speed, shield I99 will rise relatively to drum I81, thus blanking apertures I92 and I93 and exposing red aperture I94, through which the lamp Illumination on window 10 is rays pass to colour red the train speed indication on window II.

The means for automatic application of the brakes in the case of an excess of train speed over track speed is also illustrated in Figures 13 and 14. An arcuate sector 203 is formed on drum I81 as a flange thereto, and a similar arcuate sector 204 is formed on shield I99. In the inoperative position, and in positions wherein the train speed and track speed are equal, sector 203 lies above sector 204 with the gap 205 left between the two sectors. If track speed is increased over train speed, a downward displacement of shield I99 in relation to drum I81 takes place, which results in a similar relative displacement of sector 204 in relation to sector 203, and hence a widening of gap 205 occurs. Reversely, an increase of train speed over track speed results in.

Thus it will be clear that while the train speed is less than or equal to the track speed, gap 205 will bepresent and lamps I89, I90 and I9I will illuminate cell 206 to hold the brakes off. If and when train speed exceeds track speed, gap 205 is closed, and illumination on cell 2061s cut off, and the brakes are applied.

The simplification of the instrument circuit resulting from the mechanism just described is illustrated in Figure 10. The pick-up circuit with its amplifiers 51 and 65, and the proving relays 60 and 66 thereof, is unaltered. Lamps I89, I90 and HI are connected in parallel to a supply, and the track speed lamp I85 has a circuit across the supply through a proving relay 201 which when energized closes contact 208. The circuit of light-sensitive cell 206 is across the supply through a relay 209 which closes contact 2 I0 when illuminated.

From the supply a circuit is taken through contacts 208, 2 I0 and through contacts "0' and Ill of the proving relays 60 and 66 to the electro-pneumatic valve I16. While the cell 206 is illuminated from lamps I89, I and I9I (due to excess of track speed over train speed) the circuit to valve I16 is made through contact 2I0, and the brakes are held off. When, however, train speed exceeds track speed the illumination on cell 206 is interrupted, and contact 2I0 opened, thus de-energizing valve I I6 and applying the brakes with a suitable time lag.

An armature coupled to that of relay 209 closes contact 2I I when contact 2I0 is closed, and closes contact 2 I2 when contact 2I0 is open. This armature is connected across the terminals of the source of supply through a proceed repeater lamp I23 (for the use of the fireman) which is energized when cell 206 is illuminated, and a red (stop) repeater lamp I22 which is energized when the cell is not illuminated, thus indicating to the fireman that the train speed is respectively below or above the permissible track speed.

I claim:

1. An electric system of railroad signaling incorporating a plurality of segregated successive track circuits, means for circulating two electric currents in each of said track circuits, one of said currents having a frequency which is dependent upon and variable with the length, up to a predetermined maximum length, of clear track ahead of that circuit, and the other of which currents having a frequency which is dependent upon and variable with the overall physical conditions atfecting train speed of the said length of clear track, operating in combination with means, carried by a rail vehicle moving over one of said track circuits for separately picking up by induction said two currents in that track circuit, and an indicating instrument, carried by said vehicle, which is operated by said two induced currents in combination.

2. An electric system of railroad signaling according to claim 1, in which said instrument incorporates adjustment means to compensate for variation in the braking characteristics of the train embodying the rail vehicle.

3. An electric system of railroad signaling, in-

eluding a plurality of track circuits, means for passing through said track circuits two currents, the frequency of one of which is dependent upon the length of clear track ahead of said circuit up to a predetermined maximum and the frequency of the other of which is dependent upon the physical conditions aifecting the speed of the train over said length of clear track, and an instrument comprising means to indicate the maximum permissible speed of the train traveling over said track circuits, said means being manually adjustable with reference to the braking characteristics of the train; the instrument also comprising means actuated by the frequency of the physical condition current picked up by the train for automatically adjusting said indicating means and means actuated by the frequency of theclear track current picked up by the train for controlling the indication furnished by said indicating means.

4. An electric system of railroad signaling, in-

cluding a plurality of track circuits, means for the length of the clear track ahead of said circuit up to a predetermined maximum, and the frequency of the other of which isdependent upon the physical conditions affecting the speed of the train over the length of the clear track, and an instrument comprising a calibrated scale, a screen, a lamp adapted to illuminate the callbrated scale to varying heights for indicating thereby the maximum permissible track speed of a train traveling over said track, means for initially positioning the lamp with respect to the scale in accordance with the braking characteristics of the train, the instrument also comprising means actuated by the frequency of the physical condition current picked up by the train from the track circuit for automatically varying the position of said lamp from that position to which it has been initially adjusted, and means actuated by the fretrain over the length of the clear track, and an instrument comprising a calibrated scale, a screen, a lamp adapted to illuminate the calibrated scale to varying heights to indicate the maximum permissible track speed of a train traveling over said track, means for initially positioning the lamp with respect to said scale in accordance with the braking characteristics of the train, the instrument also comprising means actuated by the frequency of the physical condition current picked up by the train for automatically varying the positioning of said lamp, means actuated by the frequency of the clear track current picked up by the train for automatically adjusting said screen to control the height to which said lamp illuminates said scale, a second lamp, a second calibrated scale illuminated by said second lamp, and means for controlling the illumination of said screen by said second lamp in accordance with the actual speed of the train.

6. An electric system of railroad signaling, in cluding a plurality of track circuits, each of which is energized by two currents, the frequency of one of which is dependent upon the length of the clear track ahead of said circuit up to a predetermined maximum and the frequency of the other of which is dependent upon the physical conditions affecting train speed of the said length of clear track, an instrument comprising a callpicked upby the train for automatically moving the lamp to vary the illumination of said scale thereby, means actuated by the frequency of the clear track current picked up by the train for automatically adjusting said screen to control the height to which said lamp illuminates said scale, a second calibrated scale, and means for illuminating said second scale to a height dependent upon the actual speed of the train, and means for automatically controlling the braking of the train in accordance with relative illuminations of said scales.

7. An electric system of railroad signaling, including a plurality of track circuits each of which is energized by two currents, the frequency of one of which is dependent upon the length of clear track ahead of said circuit up to a predetermined maximum, and the frequency of the other of which is dependent upon the physical conditions affecting thetrain speed over the length of the clear track, and an instrument comprising a calibrated scale, a screen, a lamp adapted to illuminate the calibrated scale to varying heights for indicating the maximum permissible track speed of a train traveling over the track, said lamp being adjustable initially in relation to said scale in accordance with the braking characteristics of the train, the instrument also comprising means actuated by the frequency of the physical condition current picked up by the train for automatically varying the position of said lamp relatively to the scale, means actuated by the frequency of the clear track current picked up by the train for automatically adjusting said screen, whereby the height of illumination of the scale by the lamp is controlled, a second calibrated scale, means under control of the actual train of which is dependent upon the length of clear track ahead of said circuit up to a predetermined maximum and the frequency of the other of which is dependent upon the physical conditions affecting the train speed over said length of clear track, and an instrument comprising a calibrated scale, a screen, a lamp adapted to illuminate the calibrated scale to varying heights to indicate the maximum permissible track speed of a train traveling over the track, the position of the lamp being initially adjustable in relation to the scale according to the braking characteristics of the train, said instrument also comprising means actuated by the frequency of the physical condition current picked up by the train from the track circuit for automatically varying the position of said lamp, means actuated by the frequency of the clear track current picked up by the train for automatically adjusting the screen to control the height to which the scale is illuminated by the lamp, a second calibrated scale, another lamp for illuminating said second callbrated scale to varying heights in accordance with the actual speed of the train, a plurality of light sensitive strips, the resistances of which are affected respectively by the illumination projected thereon by said two lamps respectively and means for controlling a brake applying circuit in accordance with the difference in the resistances die to varying illumination of said light sensitive s rips.

9. An electric system of railroad signaling, in cluding a plurality of track circuits, each of which is energized by two currents, the frequency of one of which is dependent upon the length of clear track ahead of said circuit up to a predetermined maximum and the frequency of the other of which is dependent upon the physical condition affecting the speed of the train over the said length of clear track, and an instrument comprising a calibrated scale, a screen, a lamp adapted to illuminate the calibrated scale to varying heights in accordance with the maximum permissible track speed over the clear track ahead, means for positioning the lamp initially with respect to said scale in accordance with the braking characteristics of the train, means actuated by the frequency of the physical condition current picked up by the train for automatically varying the position of said lamp with respect to said scale, means actuated by the frequency of the clear track current picked up by the train for automatically varying the position of the screen to vary thereby the height to which said scale is illuminated by said lamp, a second calibrated scale, a second lamp, and means for illuminating said second scale by said second lamp in accordance with the actual train speed, said last named means comprising a pair of light sensitive strips, the resistances of which are affected respectively by the illumination projected thereon in accordance with the actual speed of the train and the illumination projected thereon in accordance with the permissible track speed, said light sensitive strips being adapted to energize different lamps for illuminating said second calibrated scale in varying colors dependent upon the actual train speed being below, in the zone of or above the permissible track speed respectively.

10. An electric system of railroad signaling, including a plurality of track circuits, means for passing through each track circuit two currents the frequency of one of which is dependent upon the length of clear track ahead of the circuit and the frequency of the other of which is dependent upon the over-all physical conditions aifecting the speed of the. train over the length of clear track ahead, and an instrument comprising permissible track speed indicating means, means actuated by the frequency of the clear track current picked up by the train for controlling said permissible track speed indicating means, said permissible track speed indicating means being initially adjustable in said instrument in accordance with the braking characteristics of the train, said means for actuating the track speed indicating means including a reversible electric motor, and a selectively adjustable contact device influenced by the physical condition frequency picked up by the train for controlling said electric motor.

11. An electric system of railroad signaling having a plurality of track circuits each of which is energized by two currents, the frequency of one of which is dependent upon the length of clear track ahead of the circuit and the frequency of the other of which is dependent upon the physical conditions afiecting the actual speed of the train over the clear track, and an instrument comprising a lamp, a calibrated scale for indicating thereon the maximum permissible track speed of a train, a pivoted screen adapted to be interposed at varying positions between said lamp and said scale, means actuated by the frequency of the clear track current picked up by the train for moving said screen about its pivot, and means actuated by the frequency of the physical condition current picked up by the train for varying the position of the pivot of said screen relatively to said scale.

12. An electric system of railroad signaling having a plurality of track circuits each of which is energized by two currents the frequency of one of which is dependent upon the length of clear track ahead of the circuit and the frequency of the other of which is dependent upon the physical condition affecting the actual train speed over the said length of clear track, and an instrument comprising a calibrated scale, a lamp, means under control of the frequency of the clear track current for controlling the illumination of the scale, a train speed indicator, and means for variously coloring the train speed indication dependent upon its relation to the permissible track speed, and means for automatically controlling the brakes of the train dependent upon the means for variously coloring the track and train speed indications.

13. An electric system of railroad signaling incorporating a plurality of segregated successive track circuits, means for circulating two electric currents in each of said track circuits, one of said currents having a frequency which is dependent upon and variable with the length of clear track ahead of said circuit up to a predetermined maximum and the other of which currents having a frequency which is dependent upon and variable with the over-all physical conditions affecting train speed over the length of clear track, means on a rail vehicle moving over said track circuits for separately picking up by induction said two currents in each track circuit, an indicat n instrument carried by the vehicle, means operated by the induced currents in combination for actuating said instrument to provide permissible track speed indications, and actual train speed indications, and means in said instrument for adjusting an indicating means to compensate for variation in the braking characteristics of the train embodying the rail vehicle.

14. An electric system of railroad signaling incorporating a plurality of track circuits, means for passing through each track circuit two electriccurrents, one of the currents having a frequency dependent upon the length of the clear track ahead of said circuit up to a predetermined maximum, the other of which having a frequency dependent upon the physical conditions affecting the actual speed of the train over the length of clear track, and an instrument carried by 'a rail vehicle traveling over said tracks for determining the maximum permissible speed of the train, said instrument comprising an operative unit for indicating the permissible track speed, means for adjusting said operative unit according to the braking characteristics of the train, and means operated by the frequency of said clear track circuit for controlling said operative unit within said instrument.

15. An electric system of railroad signaling incorporating a plurality of segregated track circuits, means for energizing each of said track circuits by two currents, the frequency of one of which is dependent upon the length of clear track ahead of said circuit up to a predetermined maximum and the frequency of the other of which is dependent upon the physical condition affecting the actual speed of train over the length of clear track, and an instrument carried by a rail vehicle successively traveling over the track sections with which said track circuits are associated, means in said instrument for indicating and determining the maximum permissible speed of a train traveling over the tracks, said instrument comprising an operative indicating unit, means for adjusting said unit according to the braking characteristics of the train, and means operated respectively by the frequencies of the said two currents in the segregated track sections for controlling the operative indicating unit within the instrument.

16. An electric system of railroad signaling incorporating a plurality of segregated successive track sections, circuits associated with each section, each circuit being energized by two currents the frequency of one of which is dependent upon the length of clear track ahead of said circuit up to a predetermined maximum and the frequency of the other of which is dependent upon the physical conditions affecting the actual speed of the trains over the length of clear track, and an instrument carried by a vehicle traveling over said track sections having means for determining and indicating the maximum permissible speed of a train traveling over the track, said instrument incorporating an operative unit, means for controlling the position of said operative unit, said last named means being energized by the frequency of one of said currents picked up by the rail vehicle, means for adjusting said operative unit in accordance with the braking characteristics of the train, means for determining the actual speed of the train, means for automatically indicating the relationship between the actual speed of the train and the maximum permissible track speed, and means for automatically controlling the speed of the train in accordance with the relationship between said indica- -tions.

17. An electric system of railroad signaling, incorporating in combination a plurality of segregated track circuits, means for circulating in each of said track circuits an electric current, the frequency of which is dependent upon the length of clear track ahead of that track circuit, means 

